(1) Field of the Invention
The present invention relates to a novel basic magnesium carbonate and a process for the preparation thereof. More particularly, the present invention relates to a novel basic magnesium carbonate represented by the following general formula: EQU nMgCO.sub.3.Mg(OH).sub.2.mH.sub.2 O
wherein n is a number of from 3 to 5 and m is a number of from 3 to 5,
which consists of porous particles composed of an aggregate of plate crystals having an average particle size of 2 to 50 .mu.m and a specific surface area of 10 to 70 m.sup.2 /g, wherein in the fine pore size distribution of the particles, the volume of fine pores having a radius smaller than 100 .ANG. is at least 0.02 cc/g and the volume of fine pores having a radius smaller than 75,000 .ANG. is at least 0.8 cc/g, and a process for the preparation of this novel basic magnesium carbonate.
(2) Description of the Prior Art
Basic magnesium carbonate is a known compound used for various purposes, for example, as a filler for a synthetic resin, a paper filler and a carrier for a cosmetics, medicine or agricultural chemical, and the preparation process has been known from old. In general, an aqueous slurry of a crystal of normal magnesium carbonate crystal is used as an intermediate material and is heated and aged at a temperature of 60.degree. to 80.degree. C. for 1 to several hours. After the filtration, the cake is dried at 110.degree. to 150.degree. C. Furthermore, a process for preparing spherical basic magnesium carbonate has already been proposed by us (see Japanese Unexamined Patent Publication No. 60-54915).
This spherical basic magnesium carbonate is a novel compound which is improved in powder characteristics such as the filling property, dispersibility and flowability and is advantageously used in various fields.
However, it has been found that even this spherical magnesium carbonate is not completely satisfactory as a carrier for a cosmetics, medicine or agricultural chemical.